Photographic Spectra of Stars. 375 
of the Greek alphabet in the order of refrangibility, beginning 
with the first line beyond K of the solar spectrum. The wave- 
lengths of these lines are as follows :— 
Hydrogen near Hydrogen near 
1G. 4340 | 7. 6 3767°5 
Ee 4101 8. & 3745 
ou 3 Been 3968 aL ess 3730 
A as 38875} 10. 7 3717'S 
be Be a1; 37075 
Gey. 3795 |10. 2 3699 
he spectra of the planets were taken on the plan suggested 
by the author in 1864, in which the planet’s spectrum is 
observed or photographed together with a daylight spectrum. 
These photographs show no sensible planetary modification of 
the violet and ultra-violet parts of the spectrum of the planets 
enus, Mars, and Jupiter. 
Numerous spectra of small areas of the lunar surface have 
been taken under different conditions of illumination, and dur- 
Ing eclipses of that body. The results are wholly negative as 
any absorptive action of a lunar saps 
he author is preparing to attempt to obtain by photography 
any lines which may exist in the violet and ultra-violet spectra 
of the gaseous nebulew. He also points out the suitability of 
the photographic metliod of stellar spectroscopy, first inaugu- 
tated by his researches, to some other investigations, such as— 
differences which may present themselves in the photographic 
Tegion in the case of the variable stars, the difference of rela- 
tive motion of two stars in the line of sight, the sun’s rotation 
from photographic spectra of opposite limbs, and the spectra 
of the different parts of a sun-spot. 
8 still pursuing this inquiry, he reserves an account of this 
Part of his work, 
= Messrs, Dewar and Liveing have found in their experiments similar relative 
Oise of intensity of the lines of calcium corresponding to H an in the 
*ssion spectrum of calcium. 
